Intervertebral cage designs

Abstract

Cage systems that improve upon the prior art in various ways. In the preferred embodiments, devices are radiolucent, with markers, thereby allowing visualization of placement without excessive obscuration. Devices according to the invention eliminate multiple steps, instruments and trays, while being capable of a custom fit. The devices according to the invention permit easier and greater access to end plate surface area, and can be used with autografts, allografts, and biologics.

1 .- 9 . (canceled) 
     
     
         10 . An implant for promoting intervertebral fusion, comprising:
 a cage having two sidewalls, a posterior back wall, an open top, an open bottom, and an open front; and   wherein the back wall is expandable such that the sidewalls can be brought closer together for insertion and spread apart during implantation.   
     
     
         11 . The implant of  claim 10 , wherein the side walls are substantially parallel during insertion and when spread apart. 
     
     
         12 . The implant of  claim 10 , wherein:
 the cage is comprised of two L-shaped pieces, each with a first section forming a respective one of the side walls and a second section forming a portion of the back wall; and   wherein the second sections of each L-shaped piece overlap in sliding engagement enabling the sidewalls to be brought closer together for insertion and spread apart during implantation.   
     
     
         13 . The implant of  claim 10 , wherein:
 the back wall is composed of two hinged sections hinged sections that collapse against the side walls for insertion and become substantially straightened out during implantation.   
     
     
         14 . The implant of  claim 10 , wherein each sidewall has a convex upper edge and a substantially flat lower edge, such that when viewed from the side, the upper and lower edges conform to outwardly curved and flat planes, respectively. 
     
     
         15 . The implant of  claim 10 , further including a physically separate, rigid gate element for closing the open front. 
     
     
         16 . The implant of  claim 15 , wherein the cage and gate are constructed of a radiolucent material. 
     
     
         17 . The implant of  claim 15 , wherein the cage and gate are constructed of carbon fiber. 
     
     
         18 . The implant of  claim 15 , wherein:
 the cage is constructed of a radiolucent material; and   further including one or more radiopaque markers on the cage.   
     
     
         19 . The implant of  claim 10 , wherein the backwall is indented to minimize neurocompression. 
     
     
         20 . The implant of  claim 10 , wherein:
 the sidewalls have a posterior height and an anterior height; and   wherein the posterior height is less than the anterior height, thereby forming a trapezoid.   
     
     
         21 . The implant of  claim 10 , wherein the anterior height, posterior height, or both, are sized to accommodate a particular vertebral level.